Question:

Inflammatory disease is frequently associated with anemia. At least in theory, the anemia could be partially due to stimulation of suicidal erythrocyte death or eryptosis resulting in clearance of circulating erythrocytes from circulating blood. Eryptosis is characterized by erythrocyte shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptotic erythrocytes adhere to the vascular wall by binding of phosphatidylserine to the CXC chemokine ligand 16 (CXCL16). As chronic inflammatory disease is associated with enhanced plasma levels of C-reactive protein, the present study analysed the effect of C-reactive protein on eryptosis and adhesion of erythrocytes to endothelial cells.

Methods:

Annexin V-binding was utilised to disclose PS, forward scatter to analyse cell volume, Fluo 3 fluorescence to estimate cytosolic Ca⁺² activity, CXCL16 expression utilizing western blotting, and adherence of erythrocyte to HUVEC under dynamic conditions utilizing a perfusion chamber.

Results:

Pretreatment of HUVEC with C-reactive protein up-regulated CXCL16 protein abundance. Exposure to C-reactive protein triggered erythrocyte shrinkage, and increased cytosolic Ca²⁺ activity, phosphatidylserine exposure as well as the percentage of erythrocytes adhering to HUVEC under flow conditions at arterial shear rates. Adhesion of eryptotic erythrocytes to HUVEC is blunted by coating of phosphatidylserine with annexin or of CXCL-16 with respective antibodies.

Conclusions:

exposure to C-reactive protein leads to eryptosis followed by phosphatidylserine- and CXCL16-dependent adhesion of eryptotic erythrocytes to vascular endothelial cells.